214 DR. H. GADOW ON MEXICAN [June 6, 
the Isthmus of Tehuantepec, and are restricted to Central 
America. 
Some species hate a very wide, others a very limited dis- 
tribution. The majority combine humivagous with climbing 
habits, and show great adaptiveness to the nature of their 
surroundings ; for instance, S. scalaris and S. ceneus do not climb 
the trees beneath which they live, but prefer the grassy ground, 
and they are equally at home in the moist, clouded pine-forests 
and on the more barren, grassy and lava-strewn slopes up to the 
snow-line. S. variabilis prefers the wooded lowlands of the 
Atlantic side, and likewise does not climb, loving the banks of 
rivulets and well-herbed ravines. Others, e. g. S. torquatus, are 
found only on rocks, stone walls, and buildings; they are swift. 
Some—and these are the most depressed in body—are rather 
sluggish, e.g. S. spinosus, and spend most of their time on the 
ground between spiny growth of hedges and low trees, which 
they ascend a little way, in short rapid jerks, when alarmed. 
Lastly, S. microlepidotus is truly arboreal, ascending the trees in 
the morning, with the sun, right into the green tops, where they 
hunt for insects. This species has the greatest possible alti- 
tudinal range ; from the hot country of Southern Oaxaca, only a 
few hundred feet above the level of the sea, to the upper tree-line 
of Citlaltepetl, about 13,500 feet elevation. 
Many species are viviparous. According to my own observa- 
tions, the following: acanthinus, eneus, formosus, microlepidotus, 
scalaris—all gravid in the months of July to September. 
Iguana rhinolophus is interesting for various reasons. It is 
the largest Lizard in Mexico, attaining a total length of about 
5 feet. Always arboreal and aquatic and truly tropical, it occurs 
in the whole of Central America, but in Mexico, north of the 
Isthmus, only in the States of Vera Cruz and Southern Oaxaca, 
everywhere strictly below the Plateau, and on the Pacific side it 
has been recorded only from Manzanillo near Colima and near 
Mazatlan; undoubtedly also near San Blas and in the lower 
reaches of the Balsas, but this information I have only from 
hearsay. I never found it in Guerrero. The creature requires 
permanent, rather sluggish rivers, or deep pools in the savannahs. 
They climb about in the trees, eating the succulent leaves, which 
they bolt without much chewing, for instance those of the guava 
tree. Favourite places for resting are the branches which over- 
hang the water, into which they plump with a loud splash, 
sinking at once and remaining at the bottom for many minutes. 
Whilst the adult are dusky, the young are grass-green and are 
frequently found in the tall grass at the edge of a pool. They at 
once take to the water and swim to the bottom, with their legs 
laid back and propelling themselves, like newts, by rapid undu- 
lating motions of the tail. The eggs are buried in the soft soil, 
among the roots of a tree, always near the water, in the month 
of May; by the end of July they are already hatched. They are 
known as Guanas or Iguanas. 
Ctenosaura acanthura is a common Lizard of the hot and warm 
